The present invention relates to a material testing apparatus or system that applies mechanical loads (i.e. forces and/or moments) to a test specimen. More particularly, the present invention relates to a material testing apparatus that applies multiple loads simultaneously.
The physical testing of materials by taking a test specimen and applying tension and/or compressive force loads using an actuator is well known. Commonly, a single actuator is used which, if properly controlled, can apply a single time varying uniaxial force. However, force loading upon a specimen is rarely from a single source at a single frequency. Typically, there exists multiple load sources, each of which apply time varying loads of different frequencies. Accordingly, testing machines have been developed to apply multiple uniaxial force loads simultaneously. One such testing machine is disclosed in U.S. Pat. No. 5,425,276.
Besides uniaxial testing of materials or test specimens, there is also a great need to apply simultaneous multiple mechanical loads, forces and/or moments, in a plurality of degrees of freedom. In this manner, the testing machine can more accurately simulate real life forces and moments applied to a test specimen. For instance, in order to properly perform a dynamic characterization of an engine mount for a vehicle, it is necessary to replicate or simulate as accurately as possible all forces and moments applied to the engine mount when it is mounted in a vehicle. This includes simulating the static force on the engine mount from the weight of the engine, simulating low frequency forces and moments (approximately in the range from 0 to 100 Hz) applied to the engine mount as the vehicle is driven, and simulating high frequency forces and moments (approximately in the range from 100 to 700 Hz) applied to the engine mount, for example, originating from moving components of the engine.
Testing machines have been developed to apply multiple force loads simultaneously along three orthogonal axes. The Model 833 Triaxial Test System sold by MTS Systems Corporation of Eden Prairie, Minnesota, includes flexure coupled actuators that apply force loads along three orthogonal axes to a test specimen. However, the test system cannot apply moments to the test specimen nor can the system apply high frequency loads.
Accordingly, there is a need for an improved testing apparatus that can apply simultaneous loads to a test specimen that includes moments. There is also a need for a testing apparatus that can apply high frequency mechanical loads with respect to a plurality of degrees of freedom.